Among modern structural materials fiber reinforced composites are superior. Fiber reinforced composites provide products that are low density, and high strength, and which also exhibit excellent durability and design flexibility. Thus, fiber reinforced composite materials are now widely used in industries that manufacture aircraft, automobiles, boats and ships, building materials, furniture, household products, and sports equipment to name a few.
The best quality fiber reinforced composites are made with well dispersed fiber which has a relatively long length. Not only does well dispersed fiber improve the appearance of the composite materials, the strength of fiber-reinforced materials is highest if the fiber length is long, and the fiber is well dispersed in the matrix that forms the basis of the product. Indeed, poor dispersion of fiber (fiber clumps) reduces the advantage of fiber in the composite and may even weaken the composite compared to the fiber free material.
Unfortunately, dispersing fiber uniformly is not readily accomplished with conventional technologies. Indeed, conventional technologies for fiber dispersal require high speed, high shear mixing. As a result, conventional methods risk shearing and shortening of the fibers and therefore, weakening of the composite (see e.g., U.S. Pat. No. 4,717,742 and Sanadi et al. Cellulose, Paper, and Textile Division of the American Chemical Society, Spring 1998 Newsletter (http://www.fpl.fs.fed.us/documnts/pdf1998/sanad98a.pdf). Thus, fibers are often difficult to process into composites, making quality fiber reinforced composites technically difficult to achieve, and therefore expensive to make.
Various methods have been devised in an attempt to overcome the problems associated with dispersing fiber in composite mixtures, but none have so far achieved satisfactory results. For example, U.S. Pat. No. 6,379,446 discloses methods which employ gelatinized or pre-gelatinized starch as a fiber dispersant. Although this technology disperses the fiber, unfortunately, the starch gives undesirable properties to the mixture e.g., very poor water resistance and poor stability for high temperature processing such as extrusion, injection molding and thermoforming.
Thus, there is a need in the art for quality fiber reinforced composite products, and for efficient and cost effective methods for making them.
Fortunately, the present inventors have discovered a method for substantially uniformly dispersing fiber in aqueous mixtures. Such mixtures can subsequently be used for the cost effective production of a wide array of quality fiber reinforced composite products. Thus, the invention fulfills the need for low cost, quality fiber reinforced composite products, and provides effective and cost effective methods for the production of such products.